1. Field of the Invention
The present invention relates to a gas sensor provided with a gas sensor element that detects the concentration of gas to be measured.
2. Description of the Related Art
Conventionally, as a gas sensor, a sensor which is provided with a sensor element in which electrical characteristics change depending on the concentration of a specific gas component in gas to be measured is known. Such a gas sensor is provided with, for example, a tubular metal shell which retains the sensor element, a tubular external cylinder which is swaged and fixed to the circumference of a rear end portion of the metal shell, and a seal member which is disposed in a groove portion formed in the outer peripheral surface of the metal shell.
If the gas sensor is inserted into a mounting hole formed in a mounting target body that is a target on which the gas sensor is mounted, from the front end side thereof, the seal member is deformed by being pressed against an inner wall of the mounting hole by a pressing force at the time of gas sensor mounting and performs sealing between the mounting target body and the external cylinder.
JP-A-2011-145267 is an example of the related art.
3. Problems to be Solved by the Invention
However, in general, since the metal shell is located close to the gas sensor element and made of metal, the metal shell is easily affected by heat generation of the gas sensor element. As a result, the temperature of the metal shell exceeds the heatproof temperature of the seal member made of resin, and thus a problem arises in that the durability of the seal member decreases. In order to maintain the durability of the seal member, the usage environment should be adjusted, and thus a usable environmental condition is limited.
Such a problem is a common problem arising in not only a so-called vertical type gas sensor in which a connector for extracting a signal that represents the concentration of a gas component extends along the direction of an axial line, but also in a so-called horizontal lead-out type gas sensor in which a connector extends in a direction intersecting an axial line.